Climatic drivers of tree growth in a swamp forest island in the semiarid coast of Chile

• We explore tree-ring patterns and its climate drivers in a semi-desert swamp forest.
• Myrceugenia exsucca has a time-dependent response to moisture and temperature variability.
• Climate-growth relationship shift since 1980 related to ENSO-wet anomalies.
• Swamp forests in this region are resilient to short-term climate variability.
• We provide new insights into the responses of swamp forests to increased aridity.

Isolated patches of swamp forests surrounded by xerophytic vegetation occur along the semiarid coast of Chile. Supported by shallow groundwater, these unique ecosystems have endured a long-term aridity trend during the Holocene and historical land use change. In this study, we investigated the patterns and climate drivers of annual tree growth in a coastal swamp dominated by the hygrophilous tree Myrceugenia exsucca. A tree-ring width chronology spanning the period 1864–2007 was developed and compared with long-term precipitation, temperature and soil moisture dynamics. There is a general lack of significant climate response during the earlier part of the 20th century, but a time-dependent positive growth response to temperature and moisture variability took place following partial drainage of the forest (1930s). Furthermore, a shift from a concurrent to a lagged growth response to moisture occurred around 1980, coinciding with increased frequency of ENSO-related moisture extremes. These results suggest that the ecological functioning of swamp forests in this region is very resilient to short-term climate variability, but even slight drainage disturbance can trigger very dynamic growth responses to climate variability. The degree of anthropogenic disturbance of these ecosystems will likely influence their response to projected increases in regional aridity during the coming decades.